title: Pressure-induced frustration in charge ordered spinel AlV₂O₄.
abstract: AlV2O4 is the only spinel compound so far known that exists in the charge ordered state at room temperature. It is known to transform to a charge frustrated cubic spinel structure above 427 ° C. The presence of multivalent V ions in the pyrochlore lattice of the cubic spinel phase brings about the charge frustration that is relieved in the room temperature rhombohedral phase by the clustering of vanadium into a heptamer molecular unit along with a lone V atom. The present work is the first demonstration of pressure-induced frustration in the charge ordered state of AlV2O4. Synchrotron powder x-ray diffraction studies carried out at room temperature on AlV2O4 subjected to high pressure in a diamond anvil cell show that the charge ordered rhombohedral phase becomes unstable under the application of pressure and transforms to the frustrated cubic spinel structure. The frustration is found to be present even after pressure recovery. The possible role of pressure on vanadium t2g orbitals in understanding these observations is discussed.
authors.affiliation: Condensed Matter Physics Division, Materials Science Group, Indira Gandhi Center for Atomic Research, Kalpakkam-603 102, Tamil Nadu, India.
authors.forename: S
authors.initials: S
authors.lastname: Kalavathi
authors.forename: Selva Vennila
authors.initials: SV
authors.lastname: Raju
authors.forename: Quentin
authors.initials: Q
authors.lastname: Williams
authors.forename: P Ch
authors.initials: PCh
authors.lastname: Sahu
authors.forename: V S
authors.initials: VS
authors.lastname: Sastry
authors.forename: H K
authors.initials: HK
authors.lastname: Sahu
mesh_terms: D000535:Aluminum / Q000737:chemistry*; D000537:Aluminum Oxide; D008277:Magnesium Oxide; D009556:Niobium / Q000737:chemistry*; D010087:Oxides / Q000737:chemistry*; D011312:Pressure; D013059:Spectrum Analysis, Raman; D013696:Temperature; D014639:Vanadium / Q000737:chemistry*; D014961:X-Ray Diffraction
chemical_list: D010087:Oxides; C111130:spinell; D014639:Vanadium; D009556:Niobium; C016709:pyrochlore; D008277:Magnesium Oxide; D000535:Aluminum; D000537:Aluminum Oxide